The present invention relates to a magneto-optical record medium (which will be referred to merely as a xe2x80x9cdiskxe2x80x9d hereinafter) allowing recording and reproducing of data, and also relates to a reproducing apparatus of the same.
Mini-disks are provided with grooves which correspond to waveforms of signals, produced by frequency modulation of carrier waves forming synchronous signals for rotation with address information. The grooves are utilizes for rotation control and detection of the address information. This method of recording and reproducing the information is generally referred to as a wobbling method.
It has also been proposed to employ the wobbling method in such a disk that grooves are formed similarly to the above and lands between the grooves are also used for recording.
FIG. 84 shows a structure of a disk reproducing apparatus in the prior art.
The disk reproducing apparatus shown in FIG. 84 reads out address information in the following manner. A laser beam emitted from a laser light source of an optical pickup (not shown) is divided by a diffraction grating into a main beam and side beams. When tracking control is performed to move the main beam on the center of the groove, the address information is read from push-pull signals obtained from the main beam. When the tracking control is performed to move the main beam on the center of the land, the address information recorded on the groove is read from the push-pull signals obtained from the side beam.
In the conventional disks, since data is recorded on the grooves and lands, the total length of tracks is twice as large as that of a structure in which data is recorded only on grooves. However, the address information is recorded on only the grooves. Therefore, an optical part such as a diffraction grating must be employed for dividing the laser beam, which is emitted from the laser beam source of the optical pickup, into three beams, i.e., the main beam and the two side beams as described above.
The so-called xe2x80x9cthree-beam methodxe2x80x9d in the prior art described above suffers from a problem that the power of the laser beam emitted from the laser beam source cannot be efficiently utilized.
An object of the invention is to provide a record medium, in which address information recorded by wobbling opposite sidewalls of a groove can be read out with a single laser beam in operations of recording and reproducing data with respect to not only the groove but also the land, as well as a reproducing apparatus for the same.
The object can be achieved by providing a record medium which includes an address identification portion including a land and a first groove, at least one of the land and the first groove having a variable width; and an address portion including a second groove having sidewalls wobbled in accordance with two items of address information per one data, having a constant width and connected to the first groove.
The object of the invention is also achieved by providing a reproducing apparatus for reproducing data on the above record medium, which includes a detecting circuit for irradiating the record medium with light and detecting reflected light; an address information reproducing circuit for reproducing address information in response to the reflected light detected by the detecting circuit; an address identification information reproducing circuit for reproducing the address identification information in response to the reflected light coming from the address identification portion and detected by the detecting circuit; and a select circuit for selecting one of two items of address information reproduced by the address information reproducing circuit in response to one item of the address identification information reproduced by the address identification information reproducing circuit.
As a major advantage of the invention, optical parts required in the reproducing apparatus can be reduced in number, and an intensity of a laser beam emitted to the record medium for data reproduction can be increased so that data reproduction can be achieved more reliably by the reproducing apparatus having a simpler structure than the prior art.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.